Modeling the Output Impedance of Three-Phase Uninterruptible Power Supply in D-Q Frame
The three-phase Uninterruptible Power Supply (UPS) is widely used to protect critical loads. The output impedance is a very important design specification of a UPS inverter, since the output impedance of a UPS inverter determines the voltage distortion caused by the nonlinear loads and also the stability of the whole system. This paper models the output impedance of a three-phase UPS inverter with current and voltage feedback control in d-q frame. An analytical model of UPS output impedance is derived, and experimental results are shown to verify the analysis.